Frequency distribution,Normal distribution,Mean,Median,Mode

What is the purpose of developing a frequency distribution? What is the relationship between the relative frequency and the cumulative frequency? Could a frequency distribution contain qualitative data? Why?

Describe the properties of a normal distribution. Why are there infinite possible normal distributions? Why should one assume that sample data represents a population distribution?

Do all statistical data sets have a mean, median, or mode? Why? When is the mean the best measure of central tendency? When is the median the best measure of central tendency? Explain.